Image filter processing apparatus and method

Abstract

A memory stores an output value as a filter processing result. A first calculator calculates a difference between an input value of an image signal and the output value stored in the memory. The output value is the filter processing result of a previous input value. A lookup table stores a plurality of difference values and change values, and outputs the change value corresponding to the difference calculated by the first calculator. The change value is a product of the difference and a value which is above “0” and below “1” if an absolute value of the difference is below a threshold, and the change value is a product of the difference and a value which is above “−1” and below “0” if the absolute value is above the threshold. A second calculator outputs a difference between the input value and the change value.

1. A computer system, comprising:
 a memory configured to temporarily store an output value as a filter processing result; 
 a first calculator configured to calculate a difference between an input value of an image signal and the output value stored in said memory, the output value being the filter processing result of a previous input value; 
 a lookup table configured to respectively store a plurality of differences and corresponding change values, and to output a change value corresponding to the difference calculated by said first calculator, the change value being a product of the difference and a value which is above “0” and below “1” if an absolute value of the difference is below a threshold, and the change value being a product of the difference and a value which is above “−1” and below “0” if the absolute value is above the threshold; and, 
 a second calculator configured to output a difference between the input value and the change value and to store the difference being newly stored in said memory. 
 
   
   
     2. The computer system according to  claim 1 , wherein the input value corresponds to one pixel of an image; and
 wherein the previous input value corresponds to another pixel neighboring the one pixel along the same scan line on the image. 
 
   
   
     3. The computer system according to  claim 2 , wherein the input value includes at least a luminance signal of the one pixel. 
   
   
     4. The computer system according to  claim 3 , further comprising an input terminal configured to continually input the image pixel-by-pixel along a scan direction. 
   
   
     5. The computer system according to  claim 4 , wherein said input terminal inputs the image along one of the scan directions from right to left and from left to right, and inputs the image again along the other of the scan directions. 
   
   
     6. The computer system according to  claim 4 , wherein said input terminal inputs the image along one of the scan directions from upper part to lower part and from lower part to upper part, and inputs the image again along the other of the scan directions. 
   
   
     7. The computer system according to  claim 2 , wherein said memory temporarily stores the output value of the pixel neighboring the one pixel while said input terminal inputs the image signal of the one pixel. 
   
   
     8. The computer system according to  claim 7 , wherein said first calculator subtracts the output value of the neighboring pixel from the input value of the one pixel, the subtraction result being the difference. 
   
   
     9. The computer system according to  claim 8 , wherein said second calculator subtracts the change value from the input value of the one pixel, the subtraction result being the output value of the one pixel. 
   
   
     10. A computer system, comprising:
 a noise reduction filter processing unit configured to execute a noise reduction filter processing of an input image signal; 
 a size conversion processing unit configured to execute a size conversion processing of an image signal output from said noise reduction filter processing unit; and 
 a sharpening filter processing unit configured to execute a sharpening filter processing of an image signal output from said size conversion processing unit; 
 wherein said noise reduction filter processing unit including: 
 a first memory configured to temporarily store an output value as a noise reduction filter processing result; 
 a first calculator configured to calculate a difference between an input value of the image signal and the output value stored in said first memory, the output value stored in said first memory being the noise reduction filter processing result of a previous input value of the image signal; 
 a first lookup table configured to store a plurality of differences and corresponding change values, and to output a change value corresponding to the difference calculated by said first calculator, the change value being a product of the difference and a value which is above “0” and below “1” if an absolute value of the difference is below a threshold; and 
 a second calculator configured to output a difference between the input value and the change value from the first lookup table and to store the difference in said first memory; 
 wherein said sharpening filter processing unit including: 
 a second memory configured to temporarily store an output value as a sharpening filter processing result; 
 a third calculator configured to calculate a difference between an input value from said size conversion processing unit and the output value stored in said second memory, the output value stored in said second memory being the sharpening filter processing result of a previous input value from said size conversion processing unit; 
 a second lookup table configured to store a plurality of differences and corresponding change values, and to output the change value corresponding to the difference calculated by said third calculator, the change value being a product of the difference and the value which is above “−1” and below “0” if an absolute value of the difference is above a threshold; and, 
 a fourth calculator configured to output a difference between the input value from said size conversion processing unit and the change value from the second lookup table, and to store the difference in said second memory. 
 
   
   
     11. The computer system according to  claim 10 , wherein the input value of the image corresponds to one pixel of an image, and
 wherein the previous input value of the image signal corresponds to a pixel neighboring the one pixel along the same scan line on the image. 
 
   
   
     12. The computer system according to  claim 11 , wherein the input value of the image signal includes at least a luminance signal of the one pixel. 
   
   
     13. The computer system according to  claim 12 , wherein said noise reduction filter processing unit further comprising an input terminal configured to continually input the image pixel-by-pixel along a scan direction. 
   
   
     14. The computer system according to  claim 13 , wherein said input terminal inputs the image along one of the scan directions from right to left and from left to right, and inputs the image again along the other of the scan directions. 
   
   
     15. The computer system according to  claim 13 , wherein said input terminal inputs the image along one of the scan directions from upper part to lower part and from lower part to upper part, and inputs the image again along the other of the scan directions. 
   
   
     16. The computer system according to  claim 10 , wherein said size conversion processing unit executes a magnification processing for the image signal output from said noise reduction filter processing unit. 
   
   
     17. The computer system according to  claim 13 ,
 wherein said first calculator subtracts the output value of the previous pixel from the input value of the one pixel, the output value of the previous pixel being obtained from said first memory, the input value of the one pixel being obtained from said input terminal, and 
 wherein said second calculator subtracts the change value from the input value of the one pixel, the subtraction result being input as a noise reduction filter processing result of the one pixel to said size conversion processing unit. 
 
   
   
     18. The computer system according to  claim 17 ,
 wherein said third calculator subtracts the output value of the previous pixel from the input value of the one pixel, the output value of the previous pixel being obtained from said second memory, the input value of the one pixel being obtained from said size conversion processing unit, and 
 wherein said fourth calculator subtracts the change value from the input value of the one pixel, the subtraction result being output as a sharpening filter processing result of the one pixel.